Effects of El Niño

El Niño conditions influence wintertime
atmospheric flow across the eastern
North Pacific and North America. There is
considerable event-to-event variability in the
character of El Niño episodes and in some
areas, impacts can vary substantially from

one event to another. However, there are some
sections of the United States where impacts are
fairly consistent and predictable, especially when
associated with strong El Niño episodes.

In general, El Niño results in increased precipitation
across California and the southern tier of states,
and decreased precipitation in the Pacific Northwest
and in the Ohio and Tennessee Valleys. A milder
than normal winter across the northern states and
western Canada is also a common effect. In the
eastern United States, El Niño episodes favor more
coastal storms at the expense of Alberta Clippers
(fast eastward-tracking storms across the northern
states) in winter and early spring. During the warm
season, El Niño influences hurricane development,
resulting in more eastern Pacific hurricanes and
fewer Atlantic hurricanes.